Two Dutch soldiers were killed and another seriously injured during a training exercise in Mali on Wednesday afternoon, the latest casualties in a mission that has become the most deadly place for United Nations peacekeepers to serve.

More than 11,000 soldiers are serving in the Mali mission, which aims to support the Bamako government in its fight against Islamist militants in northern Mali, who have staged assaults in the capital, as well as in Burkina Faso and Ivory Coast.

Corporal Kevin Roggeveld, 29, and sergeant Henry Hoving, 24, were killed by an exploding mortar shortly after 1130 GMT, the acting head of the Dutch armed forces told a news conference. At least 103 peacekeepers have died since the start of the mission in April 2013.

"A terrible accident took place in Mali where our soldiers are participating in the U.N. peacekeeping mission," vice-admiral Rob Bauer told reporters. A 23-year-old soldier was operated on in a field hospital before being evacuated.

Some 450 Dutch soldiers are participating in the mission to the West African country, which is meant to help implement a peace deal signed last year between Mali's government and separatist groups.

Last month, the Security Council voted to increase by 2,500 the number of peacekeepers deployed to the country, with European countries promising to send special forces and intelligence experts to support the operation.

French forces intervened in 2013 to drive back Islamist fighters who had hijacked the Tuareg uprising to seize Mali's desert north in 2012. But it has since proved difficult to prevent Islamists staging deadly attacks.

Al-Qaida in the Islamic Maghreb (AQIM) has claimed an attack on two U.N. sites in northern Mali at the end of last month, in which a peacekeeper from China and three civilians were killed and over a dozen others wounded.